Toto mods

There seems to be a good 2 or 3 inches of headroom inside the tank of my Toto Drake, has anyone ever modified the system to provide a larger more powerful flush?

Not sure if the valve can be screwed up much higher. If that were possible or it could be replaced with a standard mechanism and the overflow extended a couple of inches my guess is you could add a half gallon or more to the flush.

Alternatively I might just soup it up with something like this:
http://www.gadgets.co.uk/item/LAVNAV/LavNav-Nightlight.html

Increasing the flush volume of a low flush toilet will generall not make it work better. The trapway of that toilet is designed to flush with 1.6 gallons. What usually happens is that it will flush once, then flush again, and sometimes a third time. Kohler Wellworth models in particular can be made to triple flush. If the load went the first time, you waste the next 2 flushes. If the load doesn't go, you will overflow the bowl!

The solution is (1) use the cheapest TP you can find. Makes a big difference. Forget the Charmin! (2) get a toilet which is designed from the ground up to perform better: Toto with G-max, A/S Champion, Eljer Titan, Kohler Cimmarron, or a pressure-assist